Design guidelines for a highly efficient high-purity Germanium (HPGe)-based double-heterojunction solar cell

TL;DR

This paper presents the design and simulation of a novel high-efficiency HPGe-based double-heterojunction solar cell achieving a PCE of approximately 45.65%, leveraging optimized physical parameters and novel material combinations.

Contribution

It introduces a new n-CdS/p-HPGe/p+-BaSi2 solar cell design with detailed simulation-based optimization for high efficiency, which is a significant advancement over previous Ge-based solar cells.

Findings

Achieved a maximum PCE of ~45.65%.

High open-circuit voltage of 1.16 V.

Efficiency approaches the detailed-balance limit.

Abstract

In spite of having higher carrier mobilities and absorption coefficients of germanium (Ge) than those of silicon (Si), there has been less focus on Ge-based solar cells due to the low bandgap and high-cost of Ge wafer as well as requirement of its high-purity level. Currently, availability of high-purity Ge (HPGe), the low-cost wafer slicing method and proper design guidelines make it possible to design HPGe-based solar cells. Accordingly, in this article, we have designed and simulated a novel n-CdS/p-HPGe/p+-BaSi2 based npp+ double-heterojunction solar cell, where HPGe, cadmium sulfide (CdS) and orthorhombic barium disilicide (beta-BaSi2) have been used as the absorber, window and back-surface field (BSF) layers, respectively. Using the solar cell capacitance simulator (SCAPS-1D), the effects of different physical parameters such as the thickness, doping and defect densities, band offsets and temperature on the photovoltaic (PV) parameters of the designed solar cells have been investigated systematically. This article renders the optimized PV parameters to improve the device performance with the highest power conversion efficiency (PCE) of ~45.65% with a high open-circuit voltage of 1.16 V owing to the high built-in voltage of 1.7 V for the n-CdS/p-HPGe/p+-BaSi2 solar cells. This efficiency is almost consistent with the detailed-balance limit for double heterojunction solar cell.